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Posted on Sep 1 • Edited on Sep 2

Cognito vs IAM Identity Center: Which AWS Identity Service Should You Use?

#aws #sso #webdev #iam

As developers building modern cloud applications, managing identity and access is a critical piece of the puzzle. AWS offers two powerful services for this: Amazon Cognito and AWS IAM Identity Center. While both handle identity management, they serve distinct purposes. This post dives into their differences, use cases, and architectural patterns to help you decide which service fits your project. Let’s break it down for developers with code snippets, practical examples, and a clear decision framework.

The Core Difference in One Sentence

Amazon Cognito is a Customer Identity and Access Management (CIAM) service for authenticating and authorizing users of your web or mobile apps, while AWS IAM Identity Center is an Enterprise Identity and Access Management (EIAM) service for managing workforce access to AWS accounts and business applications.

Understanding the Services

Amazon Cognito: Your Toolkit for Customer Identity

Cognito is a developer-friendly service designed for managing external users (think customers, not employees) for your web or mobile apps. It scales effortlessly to millions of users and handles authentication, authorization, and user management with ease.

Key Components:

User Pools: Handles user sign-up, sign-in, and profile storage. Issues JSON Web Tokens (JWTs) for authenticated users, acting as an OpenID Connect (OIDC)-compliant identity provider.
Identity Pools: Exchanges JWTs for temporary AWS credentials, enabling access to AWS services like S3 or DynamoDB.

Example Use Case: A mobile app where users sign up with email/password or social logins (Google, Facebook) and access protected APIs.

Code Snippet: Setting up a Cognito User Pool client with AWS SDK for JavaScript:

import { CognitoIdentityServiceProvider } from 'aws-sdk';

const cognito = new CognitoIdentityServiceProvider();

async function createUserPoolClient() {
  const params = {
    UserPoolId: 'us-east-1_abc123',
    ClientName: 'MyAppClient',
    GenerateSecret: false,
    AllowedOAuthFlows: ['code', 'implicit'],
    AllowedOAuthScopes: ['email', 'openid'],
    CallbackURLs: ['https://myapp.com/callback'],
  };

  try {
    const response = await cognito.createUserPoolClient(params).promise();
    console.log('Client ID:', response.UserPoolClient.ClientId);
  } catch (error) {
    console.error('Error creating client:', error);
  }
}

createUserPoolClient();

Why Developers Love It:

Customization: Use hosted UI or build custom sign-in flows with Lambda triggers.
Scalability: Handles millions of users with no infrastructure management.
Integration: Works seamlessly with AWS Amplify, API Gateway, and AppSync.

Pricing: Pay-per-use based on Monthly Active Users (MAUs). Free tier includes 10,000 MAUs for direct sign-ins, but federated logins (SAML/OIDC) have a smaller free tier (50 MAUs).

AWS IAM Identity Center: Workforce Access Simplified

IAM Identity Center (formerly AWS Single Sign-On) is built for managing employee access to AWS accounts and business apps. It’s a centralized hub for enterprise identity, integrating with corporate directories like Active Directory or Okta.

Key Components:

Identity Source: Connects to internal directories or external IdPs (e.g., Okta, Microsoft Entra ID).
Permission Sets: Defines IAM roles applied across multiple AWS accounts.
SSO User Portal: A single login point for users to access all assigned AWS accounts and apps.

Example Use Case: Granting developers SSO access to multiple AWS accounts and tools like SageMaker Studio.

Code Snippet: Automating permission set creation with AWS CLI:

aws sso-admin create-permission-set \
  --instance-arn "arn:aws:sso:::instance/ssoins-1234567890abcdef0" \
  --name "DeveloperAccess" \
  --description "Read-only access for developers" \
  --session-duration "PT2H" \
  --permissions-boundary "arn:aws:iam::aws:policy/ReadOnlyAccess"

Why Developers Love It:

Centralized Management: Simplifies access control across multi-account AWS setups.
Federation: Integrates with existing corporate IdPs via SAML or SCIM.
Free: No additional cost, encouraging secure AWS adoption.

Pricing: Included at no extra charge, making it a no-brainer for enterprise AWS environments.

Head-to-Head Comparison

Attribute	Amazon Cognito	AWS IAM Identity Center
Identity Type	Customer/Application	Workforce/Employee
Primary Function	CIAM (AuthN, AuthZ, User Management)	EIAM (SSO, Centralized Access)
Target Users	Public users, customers	Employees, admins
Primary Consumer	Developers, Solutions Architects	Cloud Admins, Enterprise Architects
SSO	App federation via OIDC/SAML	SSO for AWS accounts and apps
Auth Target	Web/mobile apps, APIs	AWS Console, CLI, AWS-managed apps
Integration	Amplify, API Gateway, Lambda	AWS Organizations, Active Directory, Okta
Pricing	Per MAU	No extra charge
Customization	High (UI, Lambda triggers)	Standardized (permission sets)
Use Cases	Customer apps, SaaS, B2B	Multi-account AWS, enterprise SSO

Architectural Patterns for Developers

Cognito Patterns

Web/Mobile App Authentication

Use Case: Public-facing app with user sign-up and social logins.
Setup: Configure a User Pool for authentication and an Identity Pool for AWS resource access.
Example: A React app using AWS Amplify to handle login:

        import { Amplify, Auth } from 'aws-amplify';

        Amplify.configure({
          Auth: {
            region: 'us-east-1',
            userPoolId: 'us-east-1_abc123',
            userPoolWebClientId: 'xyz789',
          },
        });

        async function signIn(username, password) {
          try {
            const user = await Auth.signIn(username, password);
            console.log('Signed in:', user);
          } catch (error) {
            console.error('Sign-in error:', error);
          }
        }

SaaS Multi-Tenancy

Use Case: SaaS app with isolated tenant data.
Setup: Use one User Pool per tenant or a single pool with tenant IDs.

Machine-to-Machine (M2M) Authentication

Use Case: Secure microservices communication.
Setup: Use OAuth 2.0 Client Credentials Flow.

IAM Identity Center Patterns

Multi-Account Access

Use Case: Developers accessing multiple AWS accounts.
Setup: Define permission sets in the AWS Organizations management account.

Federation with Corporate IdPs

Use Case: SSO with Okta or Active Directory.
Setup: Configure SAML 2.0 or SCIM integration.

Attribute-Based Access Control (ABAC)

Use Case: Permissions based on user attributes (e.g., department).
Setup: Use tags in permission sets for dynamic access control.

Synergy: Using Cognito and IAM Identity Center Together

For advanced use cases, you can combine both services. A common pattern is using IAM Identity Center as a SAML IdP for a Cognito User Pool. This allows employees to log into a customer-facing app with corporate credentials while external users use social logins or self-registration.

Example Setup

Configure IAM Identity Center as a SAML IdP.
Link it to a Cognito User Pool.
Cognito issues JWTs for all users, unifying the token format.

Code Snippet: Configuring SAML in Cognito User Pool (AWS CLI)

aws cognito-idp create-identity-provider \
  --user-pool-id "us-east-1_abc123" \
  --provider-name "IAMIdentityCenter" \
  --provider-type "SAML" \
  --provider-details file://saml-metadata.json \
  --attribute-mapping '{"email": "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress"}'

This pattern is ideal for SaaS apps serving both internal and external users, showcasing the power of AWS’s modular identity services.

Decision Framework: Which Service to Use?

Follow this simple checklist to choose the right service:

Who are the users?

External customers → Cognito
Employees/admins → IAM Identity Center

What are they accessing?

Custom apps/APIs → Cognito
AWS Console/CLI/apps → IAM Identity Center

How are users provisioned?

Self-sign-up, social logins → Cognito
Corporate directories (Okta, AD) → IAM Identity Center

Conclusion

Amazon Cognito and AWS IAM Identity Center are complementary tools in AWS’s identity ecosystem. Cognito empowers developers to build scalable, customizable customer authentication for apps, while IAM Identity Center streamlines enterprise-grade access management for AWS environments. By understanding their strengths and combining them for advanced use cases, you can architect robust, secure identity solutions.

Pro Tip: Start with Cognito for customer-facing apps and add IAM Identity Center for workforce access as your organization scales. Experiment with the synergy pattern to unify internal and external user experiences.

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